Previous types of pressure compensating devices employing continuous integrators were used to obtain corrected volumetric gas measurements for meters, and provided for variations in the pressure and/or temperature of the fluid flow. A complete disclosure of one type of continuous integrator may be had by reference to U.S. Pat. Nos. 3,538,766 and 3,780,580.
The pressure corrections apply to a continuous integrator and are based upon Boyle's law, as follows: ##EQU1## Q = the volume of gas at a standard or base pressure. Q = THE UNCORRECTED OR ACTUAL LINE VOLUME OF GAS MEASURED BY THE METER.
A = the atmospheric pressure at the point of measurement in pounds absolute. PA1 p = the gauge pressure. PA1 Pb = the standard or base pressure in pounds absolute.
Thus, the volume of measured gas corrected to standard or base pressure will be seen to be a function of the ratio of absolute pressure at the point of measurement and at the desired standard or base pressure.
In the co-pending absolute pressure continuous integrator, use was made of a sealed evacuated bellows which served as a pressure sensing means which was located within the pressurized chamber, so as to permit the bellows to move proportionately to the level of line pressure within the chamber. In order to utilize the motion caused by the fluctuation in line pressure, a link transfer assembly is utilized to interconnect the bellows with the continuous integrator. Declining directly in absolute pressure requires that a vacuum pressure chamber be used. It therefore becomes necessary to take the link transfer assembly through a wall of the chamber in a leak-free and friction-free fashion to maintain the absolute pressure therein. In the co-pending application, this was accomplished by use of a toggle link pivoting on a pin, and being sealed by a flexible bellows. However, the range of pressure for such a construction is limited to that of 0-5 psia or slightly higher, and use of the continuous integrator at higher pressures results in frictional losses, hysteresis lag and a certain degree of non-repeatability in measurement, i.e., measurement inaccuracy.